Astronomers discover super-Earth around Barnard's star

Astronomers have discovered a planet in orbit around one of the closest stars to the Sun, Barnard's star.

The study was co-led by researchers from Queen Mary University of London, and from the Institut d'Estudis Espacials de Catalunya and the Institute of Space Sciences/CSIC in Spain.

The potentially rocky planet, known as Barnard's star b, is a 'super-Earth' with a mass of at least 3.2 times that of the Earth, and it orbits around its host star once every 233 days.

The results, published in the journal Nature, show the planet lies at a distant region from the star known as the 'snow line'. This is well beyond the habitable zone in which liquid water, and possibly life, could exist.

The planet's surface temperature is estimated to be around -170 degrees Celsius meaning it is likely to be a frozen world which is uninviting to Earth-like life.

However, if the planet has a substantial atmosphere the temperature could be higher and conditions potentially more hospitable.

Dr. Guillem Anglada Escudé, from Queen Mary's School of Physics and Astronomy, said: "Barnard's star is an infamous object among astronomers and exoplanet scientists, as it was one of the first stars where planets were initially claimed but later proven to be incorrect. Hopefully we got it right this time."


At nearly six light-years away Barnard's star is the next closest star to the Sun after the Alpha Centauri triple system.

It is a type of faint, low-mass star called a red dwarf. Red dwarfs are considered to be the best places to look for exoplanet candidates, which are planets outside our solar system.

Barnard's star b is the second closest known exoplanet to our Sun. The closest lies just over four light-years from Earth and was also discovered by a team led by Queen Mary's Dr. Anglada Escudé in 2016. That exoplanet, called Proxima b, orbits around the red dwarf star Proxima Centauri.

The researchers used the radial velocity method during the observations that led to the discovery of Barnard's star b. This technique detects wobbles in a star which are likely to be caused by the gravitational pull of an orbiting planet.

These wobbles affect the light coming from the star. As the star moves towards the Earth its spectrum appears slightly shifted towards the blue and, as it moves away, it is shifted towards the red.

This is the first time that this technique has been used to detect a planet this small so far away from its host star.

The researchers re-examined archive data obtained over a 20-year period, and added new observations with the latest generation of instruments, namely the CARMENES spectrometer in Spain, the ESO/HARPS instrument in Chile and the HARPS-N instrument in the Canary Islands.



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